A magnetron rotary cathode sputtering apparatus has a magnetic field-generating device on the inside of a cylindrical sputtering target and is designed to carry out sputtering while cooling from the inside of the target and rotating the target, and the entire surface of the target material undergoes erosion and is uniformly shaved off, whereby it is possible to obtain a remarkably high target utilization ratio (at least 60%) as compared with the utilization ratio (from 20 to 30%) of a conventional planar magnetron sputtering apparatus. Further, by rotating the target, it is possible to input a large power per unit area as compared with a conventional planar magnetron sputtering apparatus, whereby a high film deposition rate can be obtained (Patent Document 1).
As the target material for the cylindrical target to be used for the magnetron rotary cathode sputtering apparatus, a metal material is mainly used. As a ceramic material, it is strongly desired to develop e.g. ITO (indium tin oxide) or AZO (aluminum zinc oxide), but such a development has not been practically successful. One reason is “cracking” of the cylindrical target material attributable to the difference in the thermal expansion between the cylindrical target material and the cylindrical backing tube during sputtering. This is attributable to the fact that the thermal expansion coefficient of the ceramic material is usually smaller than the thermal expansion coefficient of a metal to be used as the material for the cylindrical backing tube. Once cracking takes place, particles may be formed and may adversely affect the quality of the film, or the film deposition is obliged to be stopped.
With respect to a planar target, Patent Document 2 discloses a technique with respect to the relation between cracking caused by a difference in the thermal expansion and the grinding direction on the target material. Patent Document 2 discloses that the cracking can be prevented by carrying out grinding in a direction parallel with the longitudinal direction of the planar target material (i.e. the direction in which the difference in the expansion between the planar target material and the planar substrate becomes large).
Patent Document 1: JP-A-58-500174
Patent Document 2: Japanese Patent No. 3,628,554